1. Technical Field
The present invention relates to a welding method for welded members subjected to fluoride passivation treatment, to a fluoride passivation retreatment method, and to welded products.
2. Background Art
In, for example, semiconductor manufacturing lines, because a fluorine system gas is supplied in a stable manner over a long period of time in a fluorine system gas supply line (chiefly, in fluorine system gas supply lines for excimer laser steppers), a fluoride passivated film is formed on the inner surfaces of the piping parts which comprise the fluorine gas supply system.
When members to be welded (for example, piping, valves, and the like) which are subjected to fluoride passivation treatment are welded together to produce a fluorine gas supply line, it has been discovered that the gas which is supplied from this fluorine gas supply line becomes contaminated with particles and dust (FIG. 3).
When members to be welded which have fluoride passivated films formed thereon are welded, the fluoride passivated film disappears in the welded part.
For this reason, there are occasions on which the durability with respect to fluorine system gases (chiefly, fluorine and hydrogen fluoride) worsens.
Thus, the reformation of a fluoride passivated film is conducted.
However, when welding has been conducted, even if a fluoride passivated film is again formed, the gas which is supplied from the fluorine gas supply line constructed using such welded members is contaminated by particles and dust. Furthermore, it is not always the case that the decline in durability with respect to fluorine system gases can be overcome.